actions: run dependabot monthly

Run dependabot monthly instead of weekly.

We don't really need to be running dependabot this frequently.
Monthly is also already what we're using for the website and doc-kit.

Signed-off-by: flakey5 <[email protected]>

Author: flakey5

.github/dependabot.yml

@@ -3,15 +3,15 @@ updates:
   - package-ecosystem: github-actions
     directory: '/'
     schedule:
-      interval: weekly
+      interval: monthly
     commit-message:
       prefix: chore
     open-pull-requests-limit: 10
   - package-ecosystem: npm
     directory: '/'
     versioning-strategy: increase
     schedule:
-      interval: weekly
+      interval: monthly
     commit-message:
       prefix: chore
     groups: